US4518977A - Heat-sensitive recording sheet - Google Patents

Heat-sensitive recording sheet Download PDF

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Publication number
US4518977A
US4518977A US06/531,173 US53117383A US4518977A US 4518977 A US4518977 A US 4518977A US 53117383 A US53117383 A US 53117383A US 4518977 A US4518977 A US 4518977A
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bis
sulfide
hydroxy
color
heat
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US06/531,173
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Fumio Fujimura
Toshimi Satake
Makoto Iwaguro
Toshiaki Minami
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Nippon Paper Industries Co Ltd
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Jujo Paper Co Ltd
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Assigned to JUJO PAPER CO., LTD., 4-1 OJI 1-CHOME, KITA-KU, TOKYO, JAPAN, reassignment JUJO PAPER CO., LTD., 4-1 OJI 1-CHOME, KITA-KU, TOKYO, JAPAN, ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: FUJIMURA, FUMIO, IWAGURO, MAKOTO, MINAMI, TOSHIAKI, TOSHIMI, SATAKE
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41MPRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/30Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
    • B41M5/333Colour developing components therefor, e.g. acidic compounds
    • B41M5/3333Non-macromolecular compounds
    • B41M5/3335Compounds containing phenolic or carboxylic acid groups or metal salts thereof
    • B41M5/3336Sulfur compounds, e.g. sulfones, sulfides, sulfonamides

Definitions

  • This invention relates to a heat-sensitive recording sheet having an excellent water-proofness.
  • a heat-sensitive recording sheet which utilizes a thermal color-forming reaction occurring between colorless or pale-colored chromogenic dyestuff and phenolic material, or organic acid is disclosed, for example, in the Japanese Patent Publication Nos. 4160/1968 and 14039/1970, and in the Japanese Laid-Open Patent Application No. 27736/1973, and is now widely applied for the practical use.
  • a heat-sensitive recording sheet is produced by applying the sheet surface with a coating which is prepared by individually grinding and dispersing the colorless chromogenic dyestuff and color-developing material such as phenolic substance into fine particles, mixing the resulting dispersions with each other, and then adding thereto binder, filler, sensitizer, slipping agent and other auxiliaries.
  • the coating causes instantaneously a chemical reaction which forms a color.
  • different bright colors can be advantageously formed, depending upon selection of specific colorless chromgenic dyestuff.
  • heat-sensitive recording sheets have been found in a wide range of applications, including medical or industrial measurement recording instruments, terminal printers of computer and information communication systems, facsimile equipments, printers of electronic calculators, electronic balance, automatic ticket vending machines and so on.
  • a heat-sensitive recording paper is now used in various types of tickets such as railroad tickets and admission tickets, price cards attached to the commercial goods, as well as labels.
  • the water-proofness of the recorded images has also come up to a problem depending on the cases.
  • the heat-sensitive recording paper is generally very much unstable to the water content or highly humidic condition and may reduce the density of the developed color images or even eliminate the color images due to the deposition of the water dropletes. Such an unstableness against the water is a serious problem in promoting the application of the heat-sensitive recording paper.
  • the above-mentioned object is achieved by mixing a compound represented by the following general formula (II) into a color-forming layer using a bis-(4-hydroxyphenyl) sulfide compound represented by the following general formula (I) as a color-developing agent: ##STR1## (in which R 1 represents an alkyl group with 1-4 carbon atoms or cyclohexyl group, and R 2 and R 3 individually represents an alkyl group with 1-10 carbon atoms or hydrogen atom provided that at least one of R 2 and R 3 is not hydrogen atom), ##STR2##
  • Bis-(4-hydroxyphenyl) sulfide compounds used in this invention include, for example, bis-(4-hydroxy-3-tert-butyl-6-methylphenyl)sulfide, bis-(4-hydroxy-2,5-dimethylphenyl) sulfide, bis-(4-hydroxy-2-methyl-5-ethylphenyl) sulfide, bis-(4-hydroxy-2-methyl-5-isopropylphenyl) sulfide, bis-(4-hydroxy-2,3-dimethylphenyl) sulfide, bis-(4-hydroxy-2,5-diethylphenyl)-sulfide, bis-(4-hydroxy-2,5-diisopropylphenyl) sulfide, bis-(4-hydroxy-2,3,6-trimethylphenyl) sulfide, bis-(2,4,5-trihydroxyphenyl) sulfide, bis-(4-hydroxy-2-hydroxy-2,3,6-
  • benzyl-p-benzyloxybenzoate and/or dibenzyl terephthalate are used.
  • colorless basic dyestuffs for use in this invention which are usually colorless or of pale color, various types of dyestuffs are well-known and can be used with no particular restriction.
  • the colorless fluoran type dyestuffs include the following: 3-diethyl-amino-6-methyl-7-anilinofluoran (black), 3-(n-ethyl-p-toluidino)-6-methyl-7-anilinofluoran (black), 3-diethylamino-6-methyl-7-(o-,p-dimethylanilino)-fluoran (black), 3-pyrrolidino-6-methyl-7-anilinofluoran (black), 3-piperidino-6-methyl-7-anilionofluoran (black), 3-(n-cyclohexyl-n-methylamino)-6-methyl-7-anilinofluoran(black), 3-diethylamino-7-(metha-trifluoromethylanilino)-fluoran (black), 3-dibutylamino-7-(ortho-chloroanilino)-fluoran (black), 3-diethylamino-6-methyl-chlorofluor
  • the above organic color-developing agent and the colorless basic dyestuff, as well as the compound represented by the general formula (II), are pulverized in a grinder such as a ball mill, an attritor, a sand grinder or the like, or in an appropriate emulsifying apparatus into fine particles of less than several micron particle size and mixed with various types of additives depending on the purposes to prepare a coating solution.
  • a grinder such as a ball mill, an attritor, a sand grinder or the like, or in an appropriate emulsifying apparatus into fine particles of less than several micron particle size and mixed with various types of additives depending on the purposes to prepare a coating solution.
  • the coating solution may usually be mixed with binder such as polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl-cellulose, methylcellulose, starches, styrene--maleic anhydride copolymer, vinylacetate--maleic anhydride copolymer, and styrene--butadiene copolymer, as well as organic or inorganic filler such as kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide.
  • binder such as polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl-cellulose, methylcellulose, starches, styrene--maleic anhydride copolymer, vinylacetate--maleic anhydride copolymer, and styrene--butadiene copolymer, as well as organic or inorganic filler such as kaolin, calcined kaolin, di
  • a releasing agents such as metal salt of fatty acid, lubricant such as wax, UV-absorber of benzophenone or triazole type, water-proofing agent such as glyoxal, dispersant, defoamer or the like can also be used.
  • a releasing agents such as metal salt of fatty acid, lubricant such as wax, UV-absorber of benzophenone or triazole type, water-proofing agent such as glyoxal, dispersant, defoamer or the like can also be used.
  • the kind and the amount of various ingredients for use in this invention are determined depending on the required performances and recording properties with no particular restriction. However, it is usually appropriate to use 3-10 parts of bis-(4-hydroxyphenyl)-sulfide compound, 3-12 parts of the compound represented by the above general formula (II), 1-20 parts of filler per one part of the colorless basic dyestuff, and 10-25 parts of the binder for the total solid content.
  • the oil-resistance effect can also be obtained by coating a water soluble binder on the chromophoric layer, demands for both the water-proofness and oil-resistance can be satisfied.
  • the water soluble binders usuable herein include, for instance, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, arylamide-modified polyvinyl alcohol, hydroxyethylcellulose carboxymethylcellulose and styrene--malic anhydride copolymer.
  • the heat-sensitive recording paper according to this invention Since the recorded images on the heat-sensitive recording paper according to this invention is highly water-proof, it can well withstand for the use under the circumstance where the water drops are likely to splash on during the use or under highly humidic conditions. Furthermore, the heat-sensitive recording paper is also excellent in the adaptability for the high speed recording and the blightness stability of the background color. For instance, a typical conventional heat-sensitive recording paper using bisphenol-A as a color-developing agent and fatty acid amide in combination therewith develops the color at 60°-80° C. if it is intended to be adaptable to higher speed recording, and it cannot withstand against even slight temperature increase during storage and transportation of the heat-sensitive recording paper. However, the heat-sensitive recording paper according to this invention does not reduce its brightness of the background under the temperature condition of 60°-80° C. and can provide developed color images at high density even in the high speed recording.
  • Solution A liquid dispersion of dyestuff
  • Solution B liquid dispersion of color-developing agent
  • each of the solutions having the foregoing compositions was ground in a ball mill into 3-micron particle size. Thereafter, the liquid dispersions was mixed at a ratio shown in Table 1 to form each of the coating solutions.
  • Each of the coating solutions was coated on one side of a paper of 50 g/m 2 so as to provide a coating amount of 6.0 g/m 2 and was dried.
  • the sheet was treated by a supercalender so as to obtain a smoothness for 200-300 seconds.
  • the results of the quality performance test carried out for the thus obtained black-color-developed heat-sensitive redording sheets are shown in Table 2.
  • the heat-sensitive recording sheets were pressed down for 5 seconds under pressure of 10 kg/cm 2 on the hot plate heated at 80° C., and the optical density of the pressed portion was measured by Macbeth densitometer.
  • the heat-sensitive recording sheets were left for 24 hours under severe conditions of 60° C. and 45% RH, and the brightness of the background was measured by Macbeth densitometer.
  • the heat-sensitive recording sheets recorded by Note (1) were immersed in a certain amount of water for 64 hours and dried, and then the recorded area was measured by Macbeth densitometer.
  • the heat-sensitive recording sheets obtained by the combined use of bis-(4-hydroxy-3-t-butylmethylphenyl)sulfide and benzyl p-benzyloxybenzoate or dibenzyl terephthalate provide a superior water-proofness with little reduction in optical density even for immersion in the water. It is apparent that such a superior water-proofness is a characteristic in the combined use of two compounds of this invention under consideration of comparative examples.
  • the heat-sensitive sheets of this invention provide an excellent optical density in high speed recording and superior stability of the brightness of the background. Particularly, the effect of a combined use of the bis-(4-hydroxyphenylsulfide) compound of this invention and dibenzyl terephthalate are prominent.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)

Abstract

A heat-sensitive recording sheet having a color-forming layer comprises a colorless basic dyestuff and an organic color-developing agent, in which the color-forming layer uses a bis-(4-hydroxyphenyl)sulfide compound as the color-developing agent which comprises a compound of particular structure. The sheet provides a superior water-proofness.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a heat-sensitive recording sheet having an excellent water-proofness.
2. Prior Art
A heat-sensitive recording sheet which utilizes a thermal color-forming reaction occurring between colorless or pale-colored chromogenic dyestuff and phenolic material, or organic acid is disclosed, for example, in the Japanese Patent Publication Nos. 4160/1968 and 14039/1970, and in the Japanese Laid-Open Patent Application No. 27736/1973, and is now widely applied for the practical use.
In general, a heat-sensitive recording sheet is produced by applying the sheet surface with a coating which is prepared by individually grinding and dispersing the colorless chromogenic dyestuff and color-developing material such as phenolic substance into fine particles, mixing the resulting dispersions with each other, and then adding thereto binder, filler, sensitizer, slipping agent and other auxiliaries. When this sheet is heated, the coating causes instantaneously a chemical reaction which forms a color. In this case, different bright colors can be advantageously formed, depending upon selection of specific colorless chromgenic dyestuff.
These heat-sensitive recording sheets have been found in a wide range of applications, including medical or industrial measurement recording instruments, terminal printers of computer and information communication systems, facsimile equipments, printers of electronic calculators, electronic balance, automatic ticket vending machines and so on. As the application use has become broader, a heat-sensitive recording paper is now used in various types of tickets such as railroad tickets and admission tickets, price cards attached to the commercial goods, as well as labels. On the other hand, the water-proofness of the recorded images has also come up to a problem depending on the cases. Meanwhile, the heat-sensitive recording paper is generally very much unstable to the water content or highly humidic condition and may reduce the density of the developed color images or even eliminate the color images due to the deposition of the water dropletes. Such an unstableness against the water is a serious problem in promoting the application of the heat-sensitive recording paper.
SUMMARY OF THE INVENTION
It is a general object of this invention to provide a heat-sensitive recording sheet which has an extremely high water-proofness so that the developed color images are not eliminated even when immersed in the water.
The above-mentioned object is achieved by mixing a compound represented by the following general formula (II) into a color-forming layer using a bis-(4-hydroxyphenyl) sulfide compound represented by the following general formula (I) as a color-developing agent: ##STR1## (in which R1 represents an alkyl group with 1-4 carbon atoms or cyclohexyl group, and R2 and R3 individually represents an alkyl group with 1-10 carbon atoms or hydrogen atom provided that at least one of R2 and R3 is not hydrogen atom), ##STR2##
DETAILED DESCRIPTION OF THE INVENTION
This invention will be described in detail. Bis-(4-hydroxyphenyl) sulfide compounds used in this invention include, for example, bis-(4-hydroxy-3-tert-butyl-6-methylphenyl)sulfide, bis-(4-hydroxy-2,5-dimethylphenyl) sulfide, bis-(4-hydroxy-2-methyl-5-ethylphenyl) sulfide, bis-(4-hydroxy-2-methyl-5-isopropylphenyl) sulfide, bis-(4-hydroxy-2,3-dimethylphenyl) sulfide, bis-(4-hydroxy-2,5-diethylphenyl)-sulfide, bis-(4-hydroxy-2,5-diisopropylphenyl) sulfide, bis-(4-hydroxy-2,3,6-trimethylphenyl) sulfide, bis-(2,4,5-trihydroxyphenyl) sulfide, bis-(4-hydroxy-2-cyclohexyl-5-methylphenyl)sulfide, bis-(2,3,4-trihydroxy-phenyl) sulfide, bis-(2-tert-butyl-4,5-dihydroxyphenyl)-sulfide, bis-(4-hydroxy-2,5-diphenylsulfide, bis-(4-hydroxy-2-tert-octyl-5-methylphenyl)sulfide, etc.
As a compound represented by the above general formula (II), benzyl-p-benzyloxybenzoate and/or dibenzyl terephthalate are used. As colorless basic dyestuffs for use in this invention which are usually colorless or of pale color, various types of dyestuffs are well-known and can be used with no particular restriction. For instance, the colorless fluoran type dyestuffs include the following: 3-diethyl-amino-6-methyl-7-anilinofluoran (black), 3-(n-ethyl-p-toluidino)-6-methyl-7-anilinofluoran (black), 3-diethylamino-6-methyl-7-(o-,p-dimethylanilino)-fluoran (black), 3-pyrrolidino-6-methyl-7-anilinofluoran (black), 3-piperidino-6-methyl-7-anilionofluoran (black), 3-(n-cyclohexyl-n-methylamino)-6-methyl-7-anilinofluoran(black), 3-diethylamino-7-(metha-trifluoromethylanilino)-fluoran (black), 3-dibutylamino-7-(ortho-chloroanilino)-fluoran (black), 3-diethylamino-6-methyl-chlorofluoran (red), 3-diethylamino-6-methyl-fluoran (red), 3-cyclohexyl-amino-6-chlorofluoran (orange), crystal violet lactone (blue), 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)4-azaphthalide (blue), and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-ethoxyphenyl)-3-(1-ethyl-2methylindol-3-yl)-7-azaphthalide.
The above organic color-developing agent and the colorless basic dyestuff, as well as the compound represented by the general formula (II), are pulverized in a grinder such as a ball mill, an attritor, a sand grinder or the like, or in an appropriate emulsifying apparatus into fine particles of less than several micron particle size and mixed with various types of additives depending on the purposes to prepare a coating solution. The coating solution may usually be mixed with binder such as polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl-cellulose, methylcellulose, starches, styrene--maleic anhydride copolymer, vinylacetate--maleic anhydride copolymer, and styrene--butadiene copolymer, as well as organic or inorganic filler such as kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, calcium carbonate, magnesium carbonate, and aluminum hydroxide. In addition, a releasing agents such as metal salt of fatty acid, lubricant such as wax, UV-absorber of benzophenone or triazole type, water-proofing agent such as glyoxal, dispersant, defoamer or the like can also be used. By coating the solution on a paper or various types of films, aimed heat-sensitive recording sheets can be obtained.
The kind and the amount of various ingredients for use in this invention are determined depending on the required performances and recording properties with no particular restriction. However, it is usually appropriate to use 3-10 parts of bis-(4-hydroxyphenyl)-sulfide compound, 3-12 parts of the compound represented by the above general formula (II), 1-20 parts of filler per one part of the colorless basic dyestuff, and 10-25 parts of the binder for the total solid content.
Further, since the oil-resistance effect can also be obtained by coating a water soluble binder on the chromophoric layer, demands for both the water-proofness and oil-resistance can be satisfied. The water soluble binders usuable herein include, for instance, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, arylamide-modified polyvinyl alcohol, hydroxyethylcellulose carboxymethylcellulose and styrene--malic anhydride copolymer. By the combined use with the water proofing agent, a heat-sensitive recording paper which reacts faster can be obtained.
Since the recorded images on the heat-sensitive recording paper according to this invention is highly water-proof, it can well withstand for the use under the circumstance where the water drops are likely to splash on during the use or under highly humidic conditions. Furthermore, the heat-sensitive recording paper is also excellent in the adaptability for the high speed recording and the blightness stability of the background color. For instance, a typical conventional heat-sensitive recording paper using bisphenol-A as a color-developing agent and fatty acid amide in combination therewith develops the color at 60°-80° C. if it is intended to be adaptable to higher speed recording, and it cannot withstand against even slight temperature increase during storage and transportation of the heat-sensitive recording paper. However, the heat-sensitive recording paper according to this invention does not reduce its brightness of the background under the temperature condition of 60°-80° C. and can provide developed color images at high density even in the high speed recording.
This invention will be described more specifically with an example.
EXAMPLE 1
Solution A (liquid dispersion of dyestuff)
______________________________________                                    
3-diethylamino-6-methyl-(p-chloro-                                        
                      1.5 parts                                           
anilino) fluoran                                                          
10% aqueous solution of polyvinyl                                         
                      3.4 parts                                           
alcohol                                                                   
Water                 1.9 parts                                           
______________________________________                                    
Solution B (liquid dispersion of color-developing agent)
______________________________________                                    
Bisphenol A            6 parts                                            
Aqueous 10% solution of polyvinyl                                         
                      15 parts                                            
alcohol                                                                   
Water                  9 parts                                            
______________________________________                                    
Solution C (liquid dispersion of color-developing agent)
______________________________________                                    
Bis-(4-hydroxy-3-t-butyl-                                                 
                      1.0 parts                                           
methylphenyl)sulfide                                                      
Aqueous 10% solution of polyvinyl                                         
                      2.5 parts                                           
alcohol                                                                   
Water                 1.5 parts                                           
______________________________________                                    
Solution D
______________________________________                                    
Stearic acid amide      5 parts                                           
10% aqueous solution of polyvinyl                                         
                      12.5 parts                                          
alcohol                                                                   
Water                  7.5 parts                                          
______________________________________                                    
Solution E or F
The liquid dispersion in which benzyl p-benzyloxybenzoate or dibenzyl terephthalate is used respectively instead of stearic acid amide in Solution D.
Each of the solutions having the foregoing compositions was ground in a ball mill into 3-micron particle size. Thereafter, the liquid dispersions was mixed at a ratio shown in Table 1 to form each of the coating solutions.
              TABLE 1                                                     
______________________________________                                    
Compositions of coating solution in Example 1                             
                           This                                           
       Comparative Example invention                                      
         1     2     3       4   5     1   2                              
______________________________________                                    
Solution A 6,8     6,8   6,8   6,8 6,8   6,8 6,8                          
Solution B 30      30    30    --  --    --  --                           
Solution C --      --    --    30  30    30  30                           
Solution D 25      --    --    25  --    --  --                           
Solution E --      25    --    --  25    25  --                           
Solution F --      --    25    --  --    --  25                           
           --      --    --    --  --    --  --                           
Liquid disper-                                                            
           20      20    20    20  20    20  20                           
sion of 50%                                                               
calcium carbonate                                                         
______________________________________                                    
Each of the coating solutions was coated on one side of a paper of 50 g/m2 so as to provide a coating amount of 6.0 g/m2 and was dried. The sheet was treated by a supercalender so as to obtain a smoothness for 200-300 seconds. The results of the quality performance test carried out for the thus obtained black-color-developed heat-sensitive redording sheets are shown in Table 2.
                                  TABLE 2                                 
__________________________________________________________________________
Test result for quality performance                                       
                        Stability of brightness                           
                        of background                                     
Test               Optical      60° C.,                            
                                      Water-                              
No.                                                                       
   Feature of the blend                                                   
                   density.sup.(1)                                        
                        80° C., 5 sec.sup.(2)                      
                                24 hours                                  
                                      proofness.sup.(4)                   
__________________________________________________________________________
Comparative Example                                                       
     bisphenol-A                                                          
1                  0.65 0.34    0.15  0.18                                
     stearic acid amide                                                   
     bisphenol-A                                                          
2                  1.02 0.12    0.11  0.19                                
     benzyl p-benzyloxybenzoate                                           
     bisphenol-A                                                          
3                  1.09 0.16    0.15  0.20                                
     dibenzyl terephthalate                                               
4    bis-(4-hydroxy-3-t-butyl-                                            
                   0.38 0.06    0.07  0.32                                
     methylphenyl)sulfide                                                 
5    bis-(4-hydroxy-3-t-butyl-                                            
                   0.56 0.31    0.10  0.50                                
     methylphenyl)sulfide                                                 
     stearic acid amide                                                   
This invention                                                            
1    bis-(4-hydroxyl-3-t-butyl-                                           
                   1.01 0.06    0.08  0.98                                
     methylphenyl)sulfide                                                 
     benzyl p-benzyloxybenzoate                                           
2    bis-(4-hydroxy-3-t-butyl-                                            
                   1.15 0.06    0.08  1.02                                
     methylphenyl)sulfide                                                 
     dibenzyl terephthalate                                               
__________________________________________________________________________
NOTE
(1) Optical density
Measured in a heat-sensitive facsimile apparatus, CP 6000, manufactured by TOSHIBA CORPORATION, using Macbeth densitometer for the portion evenly printed black under the condition of GIII-mode (using RD-104 amber filter, which is also used in other examples).
(2) Stability of brightness of background (80° C., 5 sec.)
The heat-sensitive recording sheets were pressed down for 5 seconds under pressure of 10 kg/cm2 on the hot plate heated at 80° C., and the optical density of the pressed portion was measured by Macbeth densitometer.
(3) Stability of brightness of the background (60° C., 24 hrs.)
The heat-sensitive recording sheets were left for 24 hours under severe conditions of 60° C. and 45% RH, and the brightness of the background was measured by Macbeth densitometer.
(4) Water-proofness
The heat-sensitive recording sheets recorded by Note (1) were immersed in a certain amount of water for 64 hours and dried, and then the recorded area was measured by Macbeth densitometer.
As apparent from Table 2, the heat-sensitive recording sheets obtained by the combined use of bis-(4-hydroxy-3-t-butylmethylphenyl)sulfide and benzyl p-benzyloxybenzoate or dibenzyl terephthalate provide a superior water-proofness with little reduction in optical density even for immersion in the water. It is apparent that such a superior water-proofness is a characteristic in the combined use of two compounds of this invention under consideration of comparative examples.
Further, the heat-sensitive sheets of this invention provide an excellent optical density in high speed recording and superior stability of the brightness of the background. Particularly, the effect of a combined use of the bis-(4-hydroxyphenylsulfide) compound of this invention and dibenzyl terephthalate are prominent.

Claims (5)

We claim:
1. A heat sensitive recording sheet having a color forming layer comprising a colorless basic dyestuff and an organic color-developing agent, said color-forming layer using a bis-(4-hydroxyphenyl) sulfide compound of the general formula (I) and a compound of the general formula (II) as a color-developing agent: ##STR3## (in which R1 represents an alkyl group with 1-4 carbon atoms or cyclohexyl group, and each of R2 and R3 represents an alkyl group with 1-10 carbon atoms or hydrogen atom, provided that at least one of R2 and R3 is not hydrogen atom), ##STR4##
2. A heat-sensitive recording sheet according to claim 1, in which the compound of the general formula (II) is dibenzyl terephthalate.
3. A heat-sensitive recording sheet according to claim 1, in which the bis-4-hydroxyphenol sulfide compound of the general formula (I) is at least one substance selected from the group consisted of bis-(4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide, bis-(4-hydroxy-2,5-dimethylphenyl)sulfide, bis-(4-hydroxy-2-methyl-5-ethylphenyl)suflide, bis-(4-hydroxy-2-methyl-5-iso-propylphenyl)sulfide, bis-(4-hydroxy-2,3-dimethylphenyl)-sulfide, bis-(4-hydroxy-2,5-diethylphenyl) sulfide, bis-(4-hydroxy-2,5-diisopropylphenyl)sulfide, bis-(4-hydroxy-2,3,6-trimethylphenyl)sulfide, bis-(2,4,5-trihydroxyphenyl)sulfide, bis-(4-hydroxy-2-cyclohexyl-5-methylphenyl) sulfide, bis-(2,3,4-trihydroxyphenyl)-sulfide, bis-(2-tert-butyl-4,5-dihydroxyphenyl)sulfide, bis-(4-hydroxy-2,5-diphenyl)sulfide, and bis-(4-hydroxy-2-tert-oxtyl-5-methylphenyl)sulfide.
4. A heat-sensitive recording sheet according to claim 1, in which the color-forming layer contains 3-10 parts by weight of bis-(4-hydroxyphenyl) sulfide compound, 3-12 parts by weight of the compound of the general formula (II), 1-20 parts by weight of filler per one part by weight of the colorless basic dyestuff, and 10-25 parts by weight of a binder for total solid content of the layer.
5. A heat-sensitive recording sheet according to claim 1, in which the color-forming layer further comprises glyoxal.
US06/531,173 1982-09-14 1983-09-08 Heat-sensitive recording sheet Expired - Fee Related US4518977A (en)

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JP57158821A JPS5964388A (en) 1982-09-14 1982-09-14 Heat sensitive recording paper

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DE3534594C2 (en) * 1984-09-28 1995-12-21 Fuji Photo Film Co Ltd Heat sensitive recording material
JPS62294588A (en) * 1986-06-13 1987-12-22 Ricoh Co Ltd Two-color thermal recording material

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US3937864A (en) * 1972-09-04 1976-02-10 Mitsubishi Paper Mills, Ltd. Heat-sensitive recording sheets having improved stability
JPS57116690A (en) * 1981-01-13 1982-07-20 Ricoh Co Ltd Thermal recording material
US4420538A (en) * 1981-01-13 1983-12-13 Murata Manufacturing Co., Ltd. Heat-sensitive recording materials

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US4020232A (en) * 1974-05-17 1977-04-26 Mitsubishi Paper Mills, Ltd. Heat-sensitive recording sheets
US4246318A (en) * 1979-04-09 1981-01-20 Appleton Papers Inc. Thermally-responsive record material
JPS5736694A (en) * 1980-08-15 1982-02-27 Mitsui Toatsu Chem Inc Heat-sensitive recording material
JPS57148688A (en) * 1981-03-11 1982-09-14 Yoshitomi Pharmaceut Ind Ltd Heat-sensitive recording paper

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US3937864A (en) * 1972-09-04 1976-02-10 Mitsubishi Paper Mills, Ltd. Heat-sensitive recording sheets having improved stability
JPS57116690A (en) * 1981-01-13 1982-07-20 Ricoh Co Ltd Thermal recording material
US4420538A (en) * 1981-01-13 1983-12-13 Murata Manufacturing Co., Ltd. Heat-sensitive recording materials

Also Published As

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GB2127572B (en) 1986-05-29
GB8324351D0 (en) 1983-10-12
DE3332844A1 (en) 1984-03-15
GB2127572A (en) 1984-04-11
JPS5964388A (en) 1984-04-12
DE3332844C2 (en) 1985-10-17
JPH0226875B2 (en) 1990-06-13

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